Finally, I came to use maps for planet modeling. Using a popular tree.js library I intend to show all new planet maps on the sphere model, along with the flat tile map. Textures for spherical models are made from image maps in the equirectangular projection. Texture files are located in the appropriate planet directories (/planets/<planetNo>/equirectangular.png and /planets/<planetNo>/equirectangular-big.png).
In the tutorials section I added a new tutorial on making maps in the equirectangular projection.